Classification of sheet material



June 23, 1964 G. w. WARREN CLASSIFICATION OF swam MATERIAL 3Sheets-Sheet 1 Original Filed Feb.

N i L INVENTOR t SEES T 1 2m 553: NM! $5.253 :8 :35

WA RREN ATTORNEYS June 23, 1964 1 5. w. WARREN 3,138,048

CLASSIFICATION OF SHEET MATERIAL Y Original Filed Feb. 24, 1956 3Sheets-Sheet 2 in 5g I .L 6/ T [in FIG 3 BY W ATTORNEYS J1me 1954 G. w.WARREN 3,138,048

-CLASSIFICATION OF SHEET MATERIAL VOL T 4 GE saunas INVENTOR 01.40;?ARREN BY MW 1 Q &- 5

ATTORNEYS United States Patent 3,138,048 CLASSIFICATION 0F SHEETMATERIAL Gladden W. Warren, Weirton, W. Va., assignor to National SteelCorporation, a corporation of Delaware Continuation of application Ser.No. 567,592, Feb. 24, 1956. This application Sept. 24, 1963, Ser. No.315,734 19 Ciairns. (Ci. 83-406) This invention relates to improvementsin classification of sheet material. More particularly the presentinvention relates to an improved apparatus for segregating prime sheetsfrom defective sheets in an arrangement in which the sheets are shearedfrom continuous strip material.

Sheet material, such as light-gage steel sheets, are formed fromcontinuous strip material fed to a shearing line which functions to cutthe strip material into sheets of predetermined length. The stripmaterial is ordinarily provided in the form of a coil supported by anuncoiling device operable to unwind the strip material and feed thestrip into the input of the shearing line which includes a shear devicefor forming the sheets. Generally, a shear device of the rotating typeis employed, and the length of the sheets produced is a function of thelinear speed of the strip material and the speed of rotation of theshear device, the shear device usually being designed to produce onesheet per revolution. Conveyor means are located at the output of theshear device for receiving the sheets and for conducting the sheets to asuitable receiver. The conveyor means may be operated at a speed greaterthan the linear speed of the strip material to space. adjacent ends ofthe sheets leaving the shear device.

In practically every instance of production of sheet material, thesheets must meet certain standards. For example, in the production ofsheets of light gage steel, the sheets must meet certain thicknessrequirements and must be free from pin holes, that is holes extendingthrough the thickness of the sheets. Also, in cases of producing sheetmaterial from coated strip, such as tinplated steel strip, the coatingmust be free from blemishes and other imperfections. The prior artincludes numerous arrangements for detecting specific characteristics orimperfections of sheet material and for segregating prime sheets fromthose sheets which include imperfections or which do not meet certainphysical requirements. It has not proven practical to scan the sheetsleaving the shear device in order to segregate prime sheets fromdefective sheets, and in lines where sheet material is formed fromcontinuous strip material the scanning or detection operation mustnecessarily take place upon the strip material on the input side of theshear device. This requirement presents a major problem of controllablydelaying signals indicative of defects in subsequently formed sheetsuntil sheets including defects reach a point in the line where thedefective or non-prime sheets may be diverted by gate means from thenormal path of the sheets and thereby segregated from the prime sheets.Since the gate means for diverting defective sheets from the normal pathof the sheets must be operated in predetermined fixed time relation withrespect to the leading edge of a defective sheet, and since a signalindication of a defective sheet may be located at any point along thelength of a defective sheet, it is not possible to merely delay thedetector signal in accordance with the strip speed and operate the gatemeans to singularly reject defective sheets.

The foregoing will be more fully understood by considering the specificproblem of detecting pin holes in sheet metal material. In arrangementsfor accomplishing this operation, a photoelectric cell type of detectoris 3,138,048 Patented June 23, 1964 Ice provided which produces a signalindicative of the presence of a pin hole. The detector is located aheadof the shear device and is positioned to scan strip materialcontinuously fed into the shear line. When a portion of strip materialincluding a pin hole passes the detector, a signal is generatedindicative of such pin hole and the signal may be delayed for a timeinterval corresponding to the time required for the detected pin hole toreach the input of a deflector gate means. However, as the pin hole maybe located at any point along the length of the sheet it is not possibleto operate the gate means responsively to the time location of the pinhole and singularly reject defective sheets in high speed lines. Inaddition to the foregoing, arrangements provided by the prior art havethe further disadvantage that they are not responsive to all pin holesor other defects in the strip material. This results from the fact thatmeans provided for delaying the signals and operating the gate meansrequires a restoring time during which the arrangement is non-responsiveto detected signals. It has been the practice in the past to solve theseproblems by operating the deflector gate means at a predetermined timeinterval following generation of a signal by the detector, and formaintaining the gate in an operative condition for a predeterminedperiod of time to allow the defective sheet, the sheet preceding thedefective sheet and the sheet following the defective sheet to passthrough the deflector gate means. The pile of defective sheets are thenvisually examined and defective sheets are manually segregated fromprime sheets. This inspection is not only time consuming and expensivebut is undesirable since pin holes may be so small as not to be detectedby visual inspection.

The present invention provides a novel arrangement operativeresponsively to detected signals, such as signals indicative of pinholes, for controlling a deflector gate in such a manner so that onlysheets of material including imperfections, such as pin holes, areallowed to pass therethrough. Thus the present invention eliminates thenecessity of rejecting two prime sheets for each defective sheet and thesubsequent time consuming operation of visually inspecting and manuallysegregating prime sheets from defective sheets.

In accordance with the broad principles of the present invention, meansare provided for converting a signal received from a detector, such as apin hole detector, from a condition indicative of the relationship ofthe pin hole relative to the strip material to a condition in which thesignal is indicative of a sheet portion of the strip material includingthe defect. The signal is then delayed for the proper period of time tocause deflector gate means to \operate in proper relationship with theleading edge of a sheet subsequently formed from the defective sheetportion to reject only the defective sheet.

The foregoing will be more fully understood from the following detaileddescription considered in connection with the accompanying drawingswhich disclose several embodiments of the invention. It is to beexpressly understood, however, that the drawings are designed forpurposes of illustration only and not as a definition of the lirm'ts ofthe invention, reference for this purpose being had to the appendedclaims.

In the drawings, in which similar reference characters denote similarelements throughout the several views:

FIG. 1 is a diagrammatic illustration of a novel sheet classifierembodying the principles of the present invention, the sheet classifierbeing shown in the environment of pin hole detection of continuous stripmaterial subsequently sheared into sheets;

FIG. 1a is an end view of a portion of FIG. 1;

FIG. 2 is an enlarged fragmentary view, in cross-section, of a portionof the sheet classifier shown in FIG. la;

FIG. 3 is a diagrammatic showing of the novel electrical circuitincluded in the sheet classifier of FIG. 1;

FIG. 4 is an enlarged fragmentary view of a portion of the apparatusprovided by the present invention; and

FIG. 5 is a diagrammatic illustration of another embodiment of theinvention.

The present invention is disclosed in FIGURE 1 of the drawings inconnection with a shear line for producing sheets from continuous stripmaterial. A coil of strip material is located at the input of the shearline and is supported by suitable uncoiling mechanism of convenentionalconstruction, not shown in the drawings. From the coil 10 the stripmaterial 11 may pass through edging cutters 12 and roller levelers 13 tothe input of a shear device 14 of the rotatable type. Suitable conveyormeans, not shown, are provided for transferring the strip material fromthe coil to the shear device. The rotary shear device 14 is showndiagrammatically as including a pair of rotary members 15 and 16,respectively, located above and below the path of the strip material 11.Each of the rotary members carries a cutting blade 17, and the cuttingblades are angularly positioned so that upon rotation of the members atthe same speed one sheet is cut upon each complete revolution. It iscommon practice to operate the shear device so that the cutting bladesmove at a speed corresponding substantially to the linear speed of thestrip material, and also to drive the rotary members 15 and 16 by meansof elliptical gearing to obtain smoother operation. Conveyors 18 and 19,which may be of the belt type, are located on the output side of theshear device. These conveyors may be operated at a speed greater thanthe linear speed of the strip material 11 to space the sheets 20 cut bythe shear device, as shown. The conveyors are spaced from each other anda deflector or reject gate 21 is located therebetween. A container 22for prime sheets is provided at the discharge end of the conveyor 19,and a container 23 for defective sheets is located beneath the deflectorgate at the discharge end of the conveyor 18. With the deflector gate 21in its position shown in FIGURE 1, sheets 20 are moved by the conveyors18 and 19 to the right, as viewed in the drawing, and are dischargedinto the prime sheet container 22. However, upon the deflector gate 21being rotated upwardly, sheets leaving the conveyor 18 are di recteddownwardly into the defective sheet container 23.

The present invention is disclosed in the environment of a system fordetecting pin holes in continuous strip ma terial fed to a shear lineand for segregating sheets having pin holes from prime sheets. It is tobe expressly understood, however, that the present invention has utilityin connection with other forms of systems, such as systems includinggages for determining sheet thickness and means for segregating off-gagesheets from on-gage sheets, for example. As shown in FIGURE 1, a pinhole detector 25 of conventional construction is located at the input ofthe shear line for scanning strip material on its Way to the sheardevice. The pin hole detector includes a light source 26 located on oneside of the path of the strip material and a photoelectric type sensingmeans 27 located on the other side of the path of the strip material.The photoelectric sensing means produces an output signal responsivelyto the presence of a pin hole in the strip material passing through thedetector, and the output signal is fed to a conventional electronicamplifier 28. The signal from the amplifier 2.8 is fed to a novel signalconverter and storage-time delay device 30. Aswill be described morefully below, the device 30 functions to convert successive signalsindicative of pin holes in the strip material into signalsrepresentative of successive portions of the strip materialcorresponding to a later formed sheet including such pin holes, and toproduce output signals therefrom in precise phase relationship withrespective sheets and delayed to effect operation of the deflector gate21 at the proper time and for the proper interval to reject only thedefective sheets.- The output 4 signals from the device 30 are fed to acontrol circuit 31 which energizes a gate operating mechanism 32connected to the deflector gate 21 through linkage 33.

The signal converterand storage-time delay device 30 includes acylindrical drum 35 which may be formed of electrical insulatingmaterial. The drum is rotatably mounted by means of a shaft 36 securedto the drum in concentric relation with its longitudinal axis andsupported in suitable bearings, not shown. One end of the shaft isconnected through a gear reduction 37 and a variable coupler 38 to therotating member 16 of the shear device 14. With this arrangement, thedrum 35 rotates in synchronism with the shear device at an integralmultiple of the speed of the shear device as determined by the gearreduction. In the arrangement illuustrated, the gear reduction providesa 10 to 1 ratio and the drum rotates at one-tenth the shear speed. Thevariable coupler 38 is provided to establish and maintain precise phaserelationship between the drum 35 and the shear cutting knives 17. Thevariable coupler is especially useful in maintaining the required phaserelationship in cases when the shear device is driven by ellipticalgears.

The drum 35 is provided with a plurality of coplanar longitudinallyspaced circumferential grooves 40, 41, 42, 43 and 44, shown more clearlyin FIGURE 2. The grooves 40, 41 and 44 receive a series A of conductivesegments 45, a series B of conductive segments 46, and a series C ofconductive segments 47, respectively. The conductive segments 45, 46 and47 are of equal arcuate length and the conductive segments of eachseries are equally spaced from each other by blocks of insulatingmaterial 48, the blocks of insulating material in each of the seriesbeing of equal arcuate' length. The grooves 42 and 43 each receive acontinuous annular band 49 and 50, respectively, of conductive material.As will appear more fully below, the series A and B of spaced conductivesegments and the continuous conductive band 49 aid in converting'signalsfrom the detector 25 and for storing and delaying the converted signalsand for feeding the output signals to the control circuit 31, while theseries C of spaced conductive segments and the continuous conductiveband 50 function to control the operating period of the deflector gate21. Also, as will be described below, the number of conductive segmentscomprising each of the series A, B and C is equal to the ratioestablished by the gear reduction 37, and the ratio is at least equal tothe nearest whole number obtained by dividing the distance between thedetector 25 and the deflector gate 21 by the length of the sheet ofsmallest dimension to be produced by the shear line.

As shown more particularly in FIGURE 3 of the drawings, the segmentscomprising the series of spaced con ductive segments A, B and C arepositioned with corresponding segments of each series in exact phaserelationship. In particular, each of the segments 45 of the series A areangularly positioned about the drum 35 in precisely the same manner ascorresponding segments 46 and 47 of the series B and C. Thus, thesegments 45, 46 or 47 of the series A, B and C are positioned so thatthe leading ends of the segments of one of the series and the leadingends of corresponding segments of the other series lie in common planesparallel to the longitudinal axis of the drum 35. Also, since thesegments of each of the series are of equal arcuate length, the trailingends of corresponding segments of each of the series lie in commonplanes parallel to the longitudinal axis of the drum. Furthermore, inaccordance with the principles of the present invention, correspondingsegments of the series are imprecise phase relationshisp with thecutting knives 17 of the shear device 14. In particular, with themembers 15 and 16 of the shear device rotated to locate the knives 17 incutting position, the drum 35 is angularly positioned so that theleading edge of corresponding segments of the series A, B and C liealong an imaginary plane represented by line X'X of FIGURE 3,

70 at the time of occurrence of the signals. 'bodiment of the inventionthe unidirectional current de- Since the drum rotates at a fixedmultiple of the shear speed, and since the number of segments of eachseries corresponds to such multiple, the arcuate lengths of the segmentsand spacers 48 are proportioned so that the leading ends of successivecorresponding segments of the series will lie along the plane XX at thetime the knives 17 of the shear device are in cutting position. Thevariable coupler 38 is operable to establish this synchronization. Therequired synchronization between the shear device and the drum may beobtained by aligning the leading edges of corresponding segments of theseries with a mark on the shear member 16 identical with the position ofthe cutting knives when in shearing position. A longitudinal bore in thedrum, in angular alignment with the leading edges of a set ofcorresponding segments of the series, may be provided as a means forsighting onto the mark on the shear member.

As shown in FIGURES 1, 2 and 3, the segments 45 of the series A areelectrically connected to corresponding segments 46 of the series Bthrough conductors each including a. unidirectional current device suchas a rectifier 60, the rectifiers being connected in the circuit toallow current flow from the segments 45 to the corresponding segments46. Also, the segments 46 of the series B are electrically connected tothe conductive band 49 through energy storage devices, such ascapacitances 61. The output of the amplifier 28 is applied across inputbrushes 70 and 71. The brush 70 is positioned to successively contactthe segments 45 of the series A upon each complete revolution of thedrum 35, and the brush 71 is mounted to continuously contact theconductive band 49. With this circuit arrangement, an output signal fromthe amplifier 28 is conducted through the brush 70, through one segment45 of the series A then contacting the brush 70, through the rectifier60 connected to the one segment 45 contacting the brush 70, and isstored in the condenser 61 connected to the corresponding segment 46 ofthe series B, the circuit being completed through the conductive band49, and the brush 71 connected to ground potential. It is to beexpressly understood that the output from the amplifier 23 occurringduring the period the input brush 70 contacts one of the segments 45 ofthe series A, which may comprise one signal or a group of signals, willbe fed to the storage capacitance 61 connected to the correspondingsegment of the series B. Also, the output from the amplifier 28occurring at a later time when the input brush 70 is in electricalcontact with a succeeding segment of the series A, will be stored in thecapacitance connected to the corresponding succeeding segment of theseries B. As shown in FIGURE 3, the input brush 70 has a dimension inthe direction of rotation of the segments 45 substantially equal to thearcuate dimension of the insulating spacers 48. Thus, the input brushwill terminate electrical contact with one of the segments 45 of theseries A and establish electrical contact with the next successivesegment of the series A substantially instantaneously.

Therefore. a series of time spaced output signals from the amplifier 28will be stored in one or more of the storage capacitances 61 dependingupon the position of the segments 45 of the series A relative to theinput brush In this emvices 6%) are provided to prevent discharge of thevoltage stored in the capacitance connected to one segment of the seriesA into the capacitance connected to the succeeding segment of the seriesA during the period in which the input brush 7t terminates electricalcontact with one segment and establishing electrical contact with thenext succeeding segment.

Output brushes 72 and 73 are provided to remove energy stored in thecapacitances 61. The brush 72 is positioned relative to the drum 35 toelectrically contact successively the segments 46 of the series B, whilethe brush 73 is mounted to continuously contact electrically theconductive band 49. As shown more clearly in FIG- URE 3, the brush 72may have a dimension in the direction of rotation of the drum 35 lessthan the arcuate dimension of the insulating spacers 48 so that thebrush 72 substantially terminates electrical contact with one of thesegments 46 before the brush 72 initiates electrical contact with thenext successive segment. Whenever the leading end of one of the segments46 moves into electrical contact with the brush 72 any voltage stored inthe capacitance connected to that segment is instantaneously developedacross the brushes 72 and 73. The brushes 72 and 73 are connected byconductors 74 and 75 in parallel with an actuating coil 76 of anelectromagnetic switch 77 included in the control circuit 31. The switch77 is connected in the grid circuit of a gaseous electron dischargedevice 78 having a control grid 79 normally biased negatively by meansof a connection to a voltage divider 80. However, upon closing of theswitch 77 the control grid 79 is biased positively and the dischargedevice 78 fires when supplied with the required plate potential. Platevoltage for the discharge device 78 is supplied from a source 81 undercontrol of the series C of segments 47. Each of the segments 47 aredirectly connected to the conductive band 50 through conductors S2. Abrush 83 is mounted relative to the drum 35 to successively electricallycontact the segments 47 upon rotation of the drum. This brush isconnected through a conductor 84 to the source of plate voltage 81. Thebrush 83, as shown more clearly in FIGURE 3, includes a dimension in thedirection of rotation of the drum slightly less than the arcuatedimension of the insulating spacers 48 so that the brush 83 terminateselectrical contact with one of the segmentss 47 before establishingelectrical contact with the next succeeding segment. A brush 85 ispositioned relative to the drum 35 to continuously contact electricallythe conductive band 50. A conductor 86 leads the brush 85 to the plate87 of the discharge device 78 in series with an actuating coil 88 of anelectromagnetic switch 39. With this arrangement whenever the switch 77closes responsively to a voltage being developed across the brushes 72and 73, the control grid '79 is positively biased and the dischargedevice 78 fires since plate voltage is at that time supplied from thesource 81 due to the phase relationship of the brushes 72 and 83 asdescribed below. The period of conduction of the discharge device 79 isdetermined by the length of the segments 47 and the speed of rotation ofthe drum 35, the discharge device 78 being extinguished upon the platevoltage dropping to Zero during transition of the brush 33 from onesegment 47 to the next succeeding segment of the series C.

The gate operating mechanism 32 includes an armature 90 mounted formovement within actuating coils 91 and 92 and being connected to thelinkage 33 for controlling operation of the deflector gate 21. Theactuating coils 91 and 92 are wound in opposition and are energized fromvoltage source E under control of an electromag netic switch 93 havingsets of contacts 94 and 95. The switch 93 is normally biased in theposition shown, by means of a spring not illustrated in the drawing, toclose the contacts 94 and connect the voltage source across theactuating coil 92. Upon energization the actuating coil 92 produces anelectromagnetic force which moves the armature 9t downwardly to closethe gate 21. The switch 93 is provided with an actuating coil 96energized from the voltage source B through a circuit including theelectromagnetic switch 89 of the control circuit 31. Upon closing of theswitch 89 responsively to firing of the discharge device 73, theactuating coil 93 is energized to open contacts 94 and close contacts95. This action energizes the coil 91 which effects upward movement ofthe armature 90 and opening of the reject gate. The reject gate remainsopen so long as current flows through the plate circuit of the dischargedevice 78 as determined by the time required for a segment 47 to movepast the brush 83.

As mentioned above, corresponding segments of each ofthe series A, B andC are located in precise phase relationship relative to each other andthe drum shaft 36 is coupled to the shear device 14 in such a manner sothat whenever the shear knives 17 are in cutting position the leadingends of correspondnig segments of each series lie in a common planepassing through the longitudinal axis of the drum. In FIGURE 3 thisplane is represented by line XX. Since one sheet is out upon eachrevolution of the shear device, and since the number of segments in eachseries is equal to the ratio established by the gear reduction 37, eachsegment of the series A, B and C is representative of a sheet portion ofthe strip material and a sheet formed from such sheet portionirrespective of the linear speed of strip material and of the length ofthe sheet. The pin hole detector 26 is located a fixed distance ahead ofthe shear device 14 and the reject gate 21 is located a fixed distancebeyond the shear device. The distances between shear device and the pinhole detector and between the shear device and the reject gate may beconverted, after the length of sheet to be cut is established, into afunction of a number of sheets. Thus, the input brush 70 is located anumber of segments ahead of the plane XX corresponding to the number ofsheets that may exist between the detector and the shear device, and thebrush 72 is located a number of segments after the plane XXcorresponding to the number of sheets between the shear device and thereject gate 21. Since the segments of the series A, B and C are ofconstant length but are representative of sheets of variable length, asdetermined by the speed of the strip material and the speed of rotationof the shear device, it is necessary to adjust the relative positions ofthe brush 70 and the brushes 72 and 83 with respect to the plane XX fordifferent lengths of sheets cut by the shear device.

A simplified structure for adjusting the brushes 70, 72 and 83 is shownin FIGURE 1 of the drawings. The brush 70 is supported by a U-shapedmember 100 having the free ends of its legs rotatably mounted about thedrum supporting shaft 36, while a U-shaped member 101, rotatablysupported on the shaft 36 in a similar manner, supports the brushes 72and 83. The brushes 70, 72 and 83 are supported by respective U-shapedmembers in such a manner as to rotate with the supporting members andyet maintain proper electrical contact with the segments of the seriesA, B and C. In one type of construction the U-shaped members maycomprise blocks of insulating material provided with a series ofopenings to receive the brushes, the blocks being rotatable about theaxes of the drum shaft and mounted with their inside surfaces in closeproximity with the exterior surface of the drum. The brush supportingmembers 100 and 101 are rigidly connected to control gears 102 and 103,and the control gears are connected through gear trains 104 and 105 to acommon gear 106 rotatable by a control knob 107. The gear trains 104 and105 may be designed so that upon rotation of the control knob in aclockwise direction the brush supporting members 100 and 101 are movedtoward each other, and upon rotation of the control knob in acounterclockwise direction the brush supporting members are moved awayfrom each other. This performance adjusts the device 30 for operationwith the particular length of sheets produced by the shear line. Thecontrol knob 107 may be calibrated with respect to the length of sheets,and in order to obtain a linear adjustment of the brushes the controlgears 102 and 103, the gear trains 104 and 105 and the common gear 106may comprise elliptical gearing. The brushes '72 and 83 are supported bythe U-shaped member 101 8 members and 101, they may be supported by themembers 100 and 101 if desired.

In the example shown in FIGURE 3 the detector 25 and the reject gate 21are positioned relative to the shear device 14 and the shear line isoperating to produce sheets 20 of such a length equal so that foursheets may exist between the detector 26 and the shear device 14 andthree sheets may exist between the shear device and the reject gate. Thecontrol knob 107 is then rotated to position the input brush 70 foursegments ahead of the plane XX, and the output brush 72 three segmentsafter the plane X-X, the gearing between the control knob and the brushsupporting members being designed in accordance with the positions ofthe detector and the reject gate relative to the shear device to providethe proper proportional movement of the brushes 70 and 72. When thecontrol knob is adjusted in accordance with the length of sheets beingproduced, the novel apparatus operates in the following manner: As theleading end of one of the segments 45 (referred to as the first segment)of the series A contacts the input brush 70, the leading edge of a sheetportion of the strip material, that is, that portion of the stripmaterial comprising a subsequently formed sheet, enters the detector 25,and as the first segment is rotated past the input brush 70 and leavescontact with the input brush the sheet portion will pass through andwill be scanned by the detector. Should a pin hole exist in any part ofthe sheet portion, the resulting signal will be amplified and fed to theinput brush 70 and passed through the first segment and its associatedrectifier to charge the storage capacitance 61 connected to thecorresponding first segment of the series B. Since the correspondingfirst segment of the series B is representative of the sheet portion thecharge on the capacitance connected thereto is representative of thesheet portion including the pin hole and the signal from the detectorindicative of a pin hole in the strip material is thereby converted intoa signal representative of a sheet portion having a pin hole. As thesheet portion having the pin hole moves from the detector towards theshear device 14, where it is cut into a sheet including the pin hole,and as the defective sheet moves toward the reject gate, itsrepresentative segment, the first segment of series B, moves across theplane XX and approaches the output brush 72. At the instant the leadingend of the first segment of the series B contacts the output brush 72,the capacitance connected to the first segment of the series B isdischarged through the actuating coil 76 to close the switch 77 andunblock the discharge device 78, and at the same instant the leading endof the corresponding first segment of the series C contacts the brush 83to provide plate voltage for the discharge device. The gaseous dischargedevice thus fires and the current flow in its plate circuit effectsclosing the switch 89 with the result that the gate operating mechanism32 funcions to open the reject gate 21. Since the first segment of theseries B is representative of the sheet including the pin hole, theoutput signal developed across the brushes 72 and 73, upon contactbetween the brush 72 and the leading end of the first segment of theseries B, is in precise phase relation with the leading edge of thedefective sheet irrespective of the location of the pin hole therein.Also, inasmuch as the input brush 70 and the output brush 72 are spacedfrom each other by a number of segments equal to the integral member ofsheets that may exist between the detector and the reject gate, theoutput signal is developed across the brushes 72 and 73 at the time theleading edge of the defective sheet approaches the reject gate. Thereject gate remains open until the trailing end of the correspondingfirst segment of the series C leaves electrical contact with the brush83 to terminate the supply of plate voltage and thereby extinguish thedischarge device 78. When the discharge device 9. is extinguished, theswitch 93 returns to its position shown in the drawing and the rejectgate is moved to closed position. Since the corresponding first segmentof the series C is also representative of the defective sheet, thereject gate will remain open for a suflicient interval to allow thedefective sheet to pass therethrough, and will then move to closedposition before the next sheet approaches the operating region of thereject gate. Inasmuch as the sheets 20 are spaced from each other delaysin operation of the reject gate due to inertia of its moving parts doesnot interfere with its performance of singularly rejecting defectivesheets. In some cases it may be desirable to cause the reject gate toopen at a fixed interval ahead of the leading edge of a defective sheet.This adjustment may be accomplished by positioning the brushes 72 and 83slightly closer to the plane XX. In particular, in the exampleillustrated in FIGURE 3, instead of positioning the brushes 72 and 83three segments ahead of the plane XX, the brushes may be positioned twoand one-half segments ahead of the plane XX to cause the reject gate toopen one-half a sheet ahead of the defective sheet. The degree thereject gate is caused to operate ahead of the leading edge of thedefective sheet may vary depending upon the type of reject gate employedand the one-half sheet lead is mentioned for exemplary purposes only.

After the first segment of the series A rotates past the input brush 70,the leading end of the next segment of the series A (referred to as thesecond segment) contacts the input brush at the time the leading edge ofthe next sheet portion enters the detector, and the second segmentrotates past the input brush in synchronism with passing of the nextsheet portion through the detector. Thereafter, successive segments ofthe series A will rotate past the input brush in synchronism withsuccessive passing of respective sheet positions through the detector.Should a pin hole exist in the strip material, the indicative signalproduced by the pin hole detector will be stored in the capacitanceconnected to the segment of the series B representative of the sheetportion including the pin hole to thereby convert the detector signalinto a signal representative of the sheet portion including the pinhole. Since each of the series A, B and C include a number of segmentsat least equal to the maximum number of sheets that may exist inend-to-end relation between the detector and the reject gate (in theshear line for which the novel apparatus is designed for operation), thedevice 35 is operable to store all converted signals representative ofsheet portions including pin holes until such converted signals aredelayed for the time interval required to effect proper operation of thereject gate and reject their representative defective sheets.Furthermore, inasmuch as the input brush 70 is provided with a dimensionin the direction of rotation of the segments 45 substantially equal tothe arcuate dimension of the insulating spacers 48, the segments of eachof the series A, B and C are effectively representative of thecontinuous strip material and the fact that the segments of each seriesare positioned in spaced end-to-end relationship does not createsuccessive voids during which the apparatus would not be responsive todetected pin holes.

Pin holes that occur in light gage steel strip may be of microscopicsize or may be quite large having dimensions along the length of thestrip up to and exceeding A1, inch. Pin hole detectors presentlyavailable produce output signals which are substantially independent ofthe size of the pin hole detected, the signal being producedresponsively to the leading portion of the pin hole. Therefore, in theevent a substantially large pin hole, having a dimension along thelength of the strip material equal to A inch, for example, is located inthe strip material on both sides of a shear cutting line, part of thepin hole would be present in the trailing edge of one sheet portion andanother part of the pin hole would be present in the leading edge of thesucceeding sheet portion. In situations of this kind, the pin holedetector would produce a signal indicative of the part of the pin holein the trailing edge of the first sheet portion and the resulting sheetwould be deflected into the compartment 23 for defective sheets;however, the detector would not produce a signal indicative of the partof the pin hole in the leading edge of the succeeding sheet portion andthe sheet formed from the succeeding sheet portion would pass into thecontainer 22 for prime sheets. In order to overcome this problem thepresent invention provides a novel arrangement for automaticallyrejecting a defective sheet and the sheet succeeding the defective sheetwhen the detected pin hole is located in a predetermined marginal regionof the trailing edge of the defective sheet. Such an arrangement insuresrejection of all defective sheets irrespective of the size and locationof the pin holes.

This feature of the invention, as shown in FIGURE 4, comprises a novelform of input brush including a pair of spaced contact elements 111 and112 adapted to successively contact the segments 45 of the series A. Theoutside edges of the elements 111 and 112 are spaced from each other adistance greater than the arcuate dimension of the insulating spacers 48so that the brush 110 simultaneously contacts the trailing edge of onesegment and the leading edge of the succeeding segment as the segments45 successively move past the brush 110. With this arrangement, when asignal from the detector occurs at a time when the brush 110simultaneously contacts a pair of adjacent segments the capacitancesconnected to the corresponding segments of series B are charged with theresult that the sheets formed from the sheet portions represented by thesignals in the charged capacitances are caused to pass through thereject gate. The extent the outside edges of the elements 111 and 112overlap the insulating spacers 48 determines the depth of the marginaledge at the trailing edge of the sheet portions in which the presence ofa pin hole will automatically eifect rejection of the next succeedingsheet. Any desired depth of marginal edge may be established as requiredand the overlap provided by the brush 110 of FIGURE 4 is for the purposeof illustration only. The rectifiers 60 connected between the segments45 of series A and corresponding segments 46 of the series B function toprevent discharge of previously charged capacitances into thecapacitance connected to the next succeeding segment when the brush 110simultaneously contacts adjacent segments.

With the segments 45 rotating in the direction indicated in the drawing,the outside edge of the element 111 comprises the trailing edge of thebrush 110 and the brush 110 is positioned so that its trailing edgeterminates electrical contact with the segments at the time the trailing edge of sheet portions leave the detector. However, since theleading edge of the brush 110, i.e., the outside edge of the element112, is spaced from the trailing edge of the brush a distance greaterthan the arcuate length of the insulating spacers 48, signals resultingfrom pin holes detected in the trailing marginal edge of the sheetportions will be passed to the capacitance representative of that sheetportion and also to the capacitance representative of the nextsucceeding sheet portion. Thus, the sheet formed from the sheet portionincluding the detected pin hole as well as the sheet formed from thesucceeding sheet portion will pass through the reject gate providing thedetected pin hole is located in the marginal trailing edge of the sheetportion as determined by the distance between the trailing and leadingedges of the brush 110.

In the embodiment of the invention shown in FIGURE 5 of the drawings,strip material 120, supported by suitable conveyor means not shown, ispassed through detector 121, such as a pin hole detector, to a sheardevice 122 whereby the strip material is formed into sheets, such assheets 123. Conveyors 124 and 125, spaced from each 11 other by a.stationary vane 126, provide a normal path for prime sheets. Theconveyor 124 comprises an endless belt 127 supported by three rolls topresent an inclined path 128 extending downwardly from the normal pathtoward the container 129 for defective sheets. A container 130 for primesheets is located at the discharge end of the conveyor 125. A signalconverter, storage and delay device includes a drum 131 rotatablysupported on a shaft 132 driven by the shear device 122 through gearreduction, not shown, so that the drum rotates at an integral multipleof the shear speed in a manner similar to the arrangement of FIGURE 1.The drum 131 carries similar series 133, 134, 135 and 136 of spacedconducting segments, the segments of each series being separated byinsulating spacers 137. The drum 131 also carries a continuousconductive band 138. The conductive segments and the insulating spacersof each of the series 133, 134,

135 and 136 may be constructed in a manner similar to the series A, Band C shown in FIGURE 1. Corresponding segments of the series 135 and136 are connected together through unidirectional current devices 139,and the segments of the series 136 are connected to the conductive band138 through capacitors 141). Corresponding segments of the series 133and 134 are interconnected by conductors 141. An input brush 142 iscarried by a rotatable supporting member 143 and is positioned tosuccessively contact the segments of the series 135 upon rotation of thedrum 131. Output brushes 144 and 145 and reject gate control brushes 146and 147 are carried by a rotatable supporting member 148 and arepositioned to respectively contact the series of segments 136, theconductive band 138, the series of segments 133 and the series ofsegments 134. The brush supporting members 143 and 148 may be adjustablyrotated by a single control knob through gear trains in a manner similarto the arrangement of FIGURE 1.

The pin hole detector 121 includes a light source 151) positioned on oneside of the path of the strip material and a photoelectric cell 151positioned on the other side of the path of the strip material. Whenlight impinges upon the photoelectric cell 151, due to the presence of apin hole in the strip material passing through the detector 121, apositive pulse is transferred through resistor 152 to the control grid153 of an electron discharge device 154 to overcome the normal blockingbias on the control grid and render the device conducting. The platecircuit of the device 154 is coupled through capacitance 155 to controlgrid 156 of a normally conducting electron discharge device 157. Thus,upon conduction of the device 154 a negative pulse is applied to thecontrol grid 156 to block the discharge device 157. When the device 157is rendered non-conducting, a positive pulse is applied throughcapacitance 158 and resistor 159 to control grid 160 of a gaseousdischarge device 161, the gaseous discharge device being biased as to beionized by the application of the positive pulse to its control grid. Acoil 162 of an electromagnetic switch 163 and contact 164 of a normallyclosed electromagnetic switch 165 are serially connected in the platecircuit of the gaseous discharge device 161, and the plate of thegaseous discharge device is coupled through capacitance 166 to controlgrid 167 of a normally conducting electron discharge device 168, theplate circuit of the latter device including coil 169 of theelectromagnetic switch 165. Upon firing of the gaseous discharge device161, current flow in its plate circuit energizes the coil 162 to closecontact 170 of the electromagnetic switch 163 and connect a source ofrelatively high voltage 171 to the input brush 142 by way of a conductor172. Current flow in the plate circuit of the gaseous discharge device161 also applies a negative pulse to the control grid 167 to block thedischarge device 168 and efifect opening of the switch 165 andextinguishment of the gaseous discharge device 161 by terminating itsplate voltage. The time constant of the capacitance 166 and the resistor173 is selected to delay blocking of the discharge device 168 to allowadequate charging of the capacitance 141) connected in the circuit withthe input brush 142.

When the drum 131 is rotated to move the leading end of a segment of'theseries 136 into contact with the output brush 144, and if thecapacitance connected to that segment is charged, a high voltagepositive pulse will appear across the output brushes 144 and 145. Thishigh voltage pulse is applied through a conductor 174 and a resistor 175to control grid 176 of a gaseous electron discharge device 177. At theinstant the output brush establishes contact with a segment of theseries 136, the brushes 146 and 147 make electrical contact withcorresponding segments of the series 133 and 134 to thereby supply platevoltage to the gaseous discharge device 177 through a conductor 178 anda coil 179 of an electromagnetic switch 1181). Simultaneous supply ofthe plate voltage and application of the positive pulse to the controlgrid 176 fires the gaseous discharge device 177, and the resultingcurrent flow in the plate circuit closes contact 181 of theelectromagnetic switch 181). The switch 181) remains closed until thegaseous discharge device 177 is extinguished upon terminating its platevoltage. The latter action occurs when the corresponding segments of theseries 133 and 134 lose contact with the brushes 146 and 147. Theelectromagnetic switch 181) controls. operation of a high currentswitching device 182 provided for controlling the flow of current fromsource 183 to a magnetic reject gate 184. The current switching device182 may comprise a pair of gaseous discharge devices 185 and 186 whichmay be of the ignition type. The magnetic reject gate 184 includes alower electromagnet 191) having a core 191 extending upwardly into closeproximity with the normal path of the sheets and positioned forward ofthe stationary vane 126, and an upper electromagnet 192 having adownwardly depending core 193. The electromagnets are elongated andextend transversely of the path of the sheets between the end rolls ofthe conveyor 124. The electromagnet 192 is connected to the source 1 83by way of conductors 188 and 194 and is continuously energized toproduce an upward force on the sheets leaving the conveyor 124 whichlifts the sheets upwardly so that they pass over the stationary vane126. The electromagnet 191), when energized, produces a downward forceon the sheets leaving the conveyor 124. The electromagnet 191) isdesigned to produce a downward force on the sheets greater than thecontinuous upward force produced by the electromagnet 192. With thisarrangement, upon energization of the electromagnet 190, the sheets aremoved downwardly to beneath the stationary vane 126 and onto theinclined conveyor 128. Energization of the electromagnet 191) iscontrolled by the high current switching device 182 responsively to theswitch 181 The switching device 182 is connected between the source 183and the electromagnet 191) by means of conductors 187 and 189. Thus,during periods of conduction of the gaseous discharge device 177, the

electromagnet is energized to pull sheets below the of the drawingsoperates in a manner similar to the arrangement shown in FIGURE 1 toconvert signals from the detector indicative of pin holes in the stripmaterial into signals representative of sheet portions including the pinholes and to store converted signals and to produce output signalsresponsively to converted signals in precise phase relationship with theleading edge of sheets formed from sheet portions, of which theconverted signals are representative, and delayed a required timeinterval to operate the reject gate and deflect respective sheets fromthe normal path of sheets leaving the shear device. The embodiment shownin FIGURE 5, however, includes novel features, not present in the FIGUREI arrangement, which improve the overall response time of the apparatusand provides a sheet classification system having a maximum speed ofoperation only limited by the operating speed of the reject gate. Theseadvantages are obtained by the provision of a pulse forming a networkfor charging the capacitances 140 responsively to signals from thedetector. The pulse forming network includes electron discharge devices161 and 168 which function, when triggered, to apply a short durationhigh voltage pulse to the circuit of the input brush 142. A triggercircuit including electron discharge devices 154 and 157 is employed totrigger the pulse forming network responsively to signals from thedetector. The circuit elements of the pulse forming network and thetrigger circuit have short time constants so that the high voltage pulseis applied to the input brush circuit substantially instantaneously uponthe presence of a signal from the detector, and the duration of the highvoltage pulse is relatively short so that the pulse forming network israpidly conditioned to respond to successive signals from the detector.The high voltage pulses stored in the capacitances are employed todirectly trigger the gaseous discharge device 177 which controls theenergizing circuit of the reject gate. With this arrangement the rejectgate is energized substantially instantaneously upon generation of theoutput signals across the brushes 144 and 145. In FIGURE the outputbrushes 146 and 147 each contact a series of spaced conductive segments133 and 134, respectively. The use of two series of spaced conductivesegments make it possible to more accurately control the operatingperiod of the reject gate 184.

Although several embodiments of the invention have been disclosed anddescribed above, it is to be expressly understood that various changesand substitutions may be made therein without departing from the spiritof the invention as well understood by those skilled in the art. Forexample, the drum 35 or 131 need not comprise a block of insulatingmaterial as previously described but may be constructed ofnon-insulating material and provided with means for insulating theconductive segments of each series from each other and from the segmentsof the other series as well as from the conductive bands. Also, otherforms of time control means may be employed for returning the gate toclosed position instead of utilizing the arrangements shown in FIGURES land 5 in which one or more series of spaced conductive segments carriedby the drum 35 or 131 are employed for this purpose. For example, thegaseous discharge devices 78 and 177 may be normally connected to asource of plate voltage through a control circuit including a normallyconducting electron discharge device having a control grid coupled tothe plate of the gaseous discharge device through a time delay circuitadjusted so that the electron discharge device of the control circuit ismomentarily blocked a predetermined period of time after the gaseousdischarge device is fired to allow a defective sheet to pass through thereject gate. Furthermore, it is contemplated by the present invention toutilize the signal converting, storing and delaying devices of FIGURES land 5 for handling signals produced by detectors in addition to pin holedetectors, such as output signals from a thickness gage, for example.Moreover, it is within the scope of the present invention to utilize thesignal converting, storage and delay devices of FIGURES 1 and 5 inconnection with a plurality of detectors for producing signalsindicative of different defects of strip material and for controllingoperation of a plurality of reject gates, one for each type of defectfor example. This may be accomplished by charging the capacitances todifferent voltages or to voltages of opposite polarity responsively tosignals indicative of different defects in the strip material. Also, inthe arrangement of FIGURES 1 and 3, the brush 83 may be adjusted to leadthe output brush 72 in order to control the operative period of thereject gate. Reference therefore will be had to the appended claims fora definition of the limits of the invention.

This application is a continuation of patent applica- 14 tion Serial No.567,592, filed February 24, 1956, now abandoned.

What is claimed is:

1. In a shear line for continuous strip material including a shear forcutting successive sheet portions of continuous strip material intosheets of predetermined length and deflector means operable to directsheets along a predetermined path, the combination comprising detectormeans for detecting defects in the strip material on its way to theshear and producing signals indicative of such defects, a series ofisolated energy storage means each indicative of a single sheet portionof the continuous strip material, means for successively coupling thedetector means to isolated energy storage means of the series insynchronism with successive movement of sheet portions of the stripmaterial relative to the detector means whereby signals from thedetector means indicative of defects in sheet portions of the stripmaterial are stored in separate isolated energy storage means, means forsuccessively removing signals from isolated energy storage means inphase with a predetermined point along the length of sheets formed fromrespective sheet portions of the strip material and delayed to coincidewith the time respective sheets approach the deflector means, and meansfor operating the deflector means responsively to removed signals.

2. In a shear line for continuous strip material including a shear forcutting successive sheet portions of continuous strip material intosheets of predetermined length and deflector means operable to directsheets along a predetermined path, the combination comprising detectormeans positioned relative to the path of the strip material on its wayto the shear detecting defects in the strip material and producingsignals indicative of such defects, a series of spaced conductivemembers each indicative of a single sheet portion of the continuousstrip material, an input brush mounted to successively contact theconductive members of the series upon relative movement between theinput brush and the series of conductive members, means for feedingsignals produced by the detector means to the input brush, an energystorage element connected to each conductive member of the series ofconductive members, means for synchronizing relative movement betweenthe input brush and the series of conductive members and movement ofsheet portions relative to the detector means so that the input brushsuccessively moves relative to the conductive members in synchronismwith movement of sheet portions relative to the detector means, meansfor adjusting the phase of the relative movement of the input brush andthe series of spaced conductive members and the movement of sheetportions relative to the detector means so that electrical contact isestablished between the input brush and the leading end of a conductivemember at the time the leading edge of a sheet portion enters thedetector means, and means for removing signals from the storage elementsin synchronism with sheets formed from respective sheet portions whichare delayed to operate the deflector means at the proper time to deflectdefective sheets along the predetermined path.

3. The combination defined in claim 2 in which unidirectional currentmeans are provided in the connection between each of the conductivemembers and the storage element connected thereto.

4. The combination defined in claim 3 in which the input brush has adimension in the direction of movement relative to the series of spacedconductive members greater than the space between the conductivemembers.

5. Means for controlling the movement of sheet material between firstand second paths comprising conveyor means for conducting the sheetmaterial toward the first and second paths, a stationary memberpositioned in the region between the conveyor means and the first andsecond paths, continuously energized first electromagentic meanspositioned in the region of the forward end of the stationary member andspaced above the stationary member to apply an upward force on sheetmaterial leaving the conveyor means and lift the sheet material to abovethe stationary member, a secondelectromagnetic means located in theregion of the forward end of the stationary member and spaced below thestationary member operable when energized to apply a downward force onsheet material leaving the conveyor means and pull the sheet material tobelow the stationary member, and means for energizing the secondelectromagnetic means, the second electromagnetic means when energizedproducing a downward force on sheet material greater than the upwardforce continuously produced by the first electromagnetic means.

6. Means for controlling movement of sheet material between first andsecond paths comprising conveyor means for conducting the sheet materialtoward the first and second paths, the conveyor means and the first pathlying in a substantially common plane, a stationary vane memberpositioned in the region between the conveyor means and the first andsecond paths, the vane member lying in the common plane and above thesecond path, continuously energized first electromagnetic meanspositioned in the region of the forward end of the stationary vanemember and spaced above the stationary vane member to apply an upwardforce on sheet material leaving the conveyor means and lift the sheetmaterial to above the stationary vane member, a second electromagneticmeans located in the region of the forward end of the stationary vanemember and spaced below the stationary vane member operable whenenergized to apply a downward force on sheet material leaving theconveyor means and pull the sheet material to below the stationary vanemember, and means for energizing the second electromagnetic means, thesecond electromagnetic means when. energized producing a downward forceon sheet material greater than the upward force continuously produced bythe first electromagnetic means.

7. In a shear line for continuous strip material including a shear forcutting successive sheet portions of continuous strip material intosheets of predetermined length and deflector means operable to directsheets along a predetermined path, the combination comprising means fordetecting defects in the strip material on its way to the shear andproducing signals indicative of such defects, a series of isolatedenergy storage elements each indicative of a single sheet portion of thecontinuous strip material, coupling means for successively connectingthe output of the detector means to isolated energy storage elements ofthe series at a frequency corresponding to the frequency at which sheetportions pass the detector means, means for synchronizing the couplingmeans so that the output of the detector means is connected to a storageelement at the time the leading edge of a sheet portion approaches thedetecor means whereby signals from the detector means indicative ofdefects in the sheet portions of the strip material are stored inseparate isolated energy storage elements, means for removing signalsfrom the series of isolated energy storage elements at a rate corresponding to the rate defective portions move relative to the detectormeans in synchronism with sheets formed from respective sheet portions,and means for operating the deflector means responsively to the removedsignals, the removed signals being delayed to operate the deflectormeans at the proper time to direct defective sheets along thepredetermined path.

8. In a shear line for continuous material including a shear for cuttingsuccessive sheet portions of continuous material into sheets ofpredetermined length and deflector means operable to direct sheets alonga predetermined path, comprising detector means for detecting a defectin the continuous material and producing a signal indicative of saiddefect, energy storage means, means for passing said signal indicativeof said defect to the energy storage means, means including the energystorage means for producing a signal indicative of a single sheetportion of the continuous material having said defect in response topassing to the energy storage means of said signal indicative of saiddefect, and means for operating the deflector means responsively to thesignal indicative of a single sheet portion of the continuous materialhaving said defect to direct a sheet having said defect along thepredetermined path.

9. Apparatus for inspecting and shearing successive sheet portions ofcontinuous material into sheets and classifying the sheets in accordancewith a characteristic of the material determined while the material isin continuous form including a shear for forming sheets from sheetportions of the continuous material, guide means for guiding thecontinuous material to the shear, means for conveying sheets formed fromthe continuous material away from the shear, and deflecting meanslocated in the path of travel of shets conveyed away from the shear fordeflecting sheets along a predetermined path in accordance with acharacteristic of the sheets determined when the material is incontinuous form, comprising detecting means located along the guidemeans in advance of the shear for producing an output signal in responseto a characteristic of the material in continuous form, means responsiveto the output signal of the detecting means for determining the sheetportion of the continuous material including said characteristic, meanssynchronized with the shear for following movement of said sheet portionalong the guide means to the shear, means responsive to the last-namedmeans for producing a control signal indicative of the sheet formed fromsaid sheet portion, and means responsive to the control signal foroperating the deflecting means to deflect said sheet along thepredetermined path.

10. Apparatus for inspecting and shearing successive sheet portions ofcontinuous material into sheets and classifying the sheets in accordancewith a characteristic of the material determined while the material isin continuous form including a shear for forming sheets from sheetportions of the continuous material, guide means for guiding thematerial in continuous form to the shear, means for conveying sheetsformed from the continuous material away from the shear, and deflectingmeans located in the path of travel of sheets conveyed away from theshear for deflecting sheets along a predetermined path in accordancewith a characteristic of the sheets determined when the material is incontinuous form, comprising detecting means located along the guidemeans in advance of the shear for producing an output signal in responseto a characteristic of the material in continuous form, means responsiveto the output signal of the detecting means for producing a signalindicative of the sheet portion of the continuous material includingsaid characteristic, means for advancing in time a signal indicative ofsaid sheet portion including said characteristic in synchronism withmovement of said sheet portion along the guide means from the detectingmeans to the shear, means responsive to the advanced signal forproducing a control signal indicative of the sheet formed from saidsheet portion, and means operative responsively to the control signalfor operating the deflecting means to direct said sheet along thepredetermined path.

No references cited

1. IN A SHEAR LINE FOR CONTINUOUS STRIP MATERIAL INCLUDING A SHEAR FORCUTTING SUCCESSIVE SHEET PORTIONS OF CONTINUOUS STRIP MATERIAL INTOSHEETS OF PREDETERMINED LENGTH AND DEFLECTOR MEANS OPERABLE TO DIRECTSHEETS ALONG A PREDETERMINED PATH, THE COMBINATION COMPRISING DETECTORMEANS FOR DETECTING DEFECTS IN THE STRIP MATERIAL ON ITS WAY TO THESHEAR AND PRODUCING SIGNALS INDICATIVE OF SUCH DEFECTS, A SERIES OFISOLATED ENERGY STORAGE MEANS EACH INDICATIVE OF A SINGLE SHEET PORTIONOF THE CONTINUOUS STRIP MATERIAL, MEANS FOR SUCCESSIVELY COUPLING THEDETECTOR MEANS TO ISOLATED ENERGY STORAGE MEANS OF THE SERIES INSYNCHRONISM WITH SUCCESSIVE MOVEMENT OF SHEET PORTIONS